Display devices containing low molecular weight liquid crystals as display elements have been widely used for digital display of desk calculators, clocks and watches, etc. In these fields of utilization, the conventional low molecular weight liquid crystals are generally interposed between a couple of glass substrates which are arranged with a separation distance adjusted in micron unit. However, such an adjustment of the space has been practically impossible in the production of displays with a large picture plane or a bent picture plane. In order to solve the problem, some attempts have been made to develop polymeric liquid crystals so as to render liquid crystals themselves moldable (for example, J. Polym., Sci, Polym., Lett., Ed. 13, 243 (1975), Polym., Bull., 6, 309 (1982), Japanese Patent Application Kokai Koho (Laid-open) No. 56-21479).
These polymeric liquid crystals, however, have a defect that they do not exhibit properties of liquid crystals at room temperature unless they are heated to a temperature not lower than the glass transition temperatures thereof and lower than the clearing temperatures thereof in order to transit them into a liquid crystal state.
Japanese Patent Application Kokai Koho (Laid-open) No. 63-99204 reports the synthesis of polyacrylate-type ferroelectric liquid-crystalline polymers and shows that they are improved in performances as compared with the above-described polymeric liquid crystals. Nevertheless, even these side-chain type polymeric liquid crystals are unsatisfactory in their response speeds and the temperature ranges in which they can function.
In Japanese Patent Application Kokai Koho (laid-open) No. 63-254529 are disclosed polyether-type ferroelectric polymeric liquid crystals obtainable by polymerizing epoxy monomers, for example polymeric liquid crystals which are represented by the following formula ##STR4## wherein s is an integer of 1 to 30,
and are obtained by polymerizing epoxy compounds represented by the following formula ##STR5## Although the side-chain type polymeric liquid crystals have an advantageous capability to respond to stimulations with external electric fields at a wide range of temperature including room temperature or the vicinity, they are still insufficient for practical use.
An object of the present invention is to provide a novel polymeric liquid crystal which not only exhibits ferroelectricity at a wide range of temperature including room temperature but also responds to external electric fields at great speed.
Another object of the present invention is to provide a process for the preparation of the polymeric liquid crystal, a diene compound usable for the preparation of the polymeric liquid crystals and a process for the preparation of the diene compound.